Flow Triggering Research Articles

A self-regulated expiratory flow device for mechanical ventilation: a bench study

IntroductionUnregulated expiratory flow may contribute to ventilator-induced lung injury. The amount of energy dissipated into the lungs with tidal mechanical ventilation may be used to quantify potentially injurious ventilation. Previously reported devices for variable expiratory flow regulation (FLEX) require, either computer-controlled feedback, or an initial expiratory flow trigger. In this bench study we present a novel passive expiratory flow regulation device.MethodsThe device was tested using a commercially available mechanical ventilator with a range of settings (tidal volume 420 ml and 630 ml, max. inspiratory flow rate 30 L/min and 50 L/min, respiratory rate 10 min−1, positive end-expiratory pressure 5 cmH2O), and a test lung with six different combinations of compliance and resistance settings. The effectiveness of the device was evaluated for reduction in peak expiratory flow, expiratory time, mean airway pressure, and the reduction of tidal dissipated energy (measured as the area within the airway pressure–volume loop).ResultsMaximal and minimal reduction in peak expiratory flow was from 97.18 ± 0.41 L/min to 25.82 ± 0.07 L/min (p < 0.001), and from 44.11 ± 0.42 L/min to 26.30 ± 0.06 L/min, respectively. Maximal prolongation in expiratory time was recorded from 1.53 ± 0.06 s to 3.64 ± 0.21 s (p < 0.001). As a result of the extended expiration, the maximal decrease in I:E ratio was from 1:1.15 ± 0.03 to 1:2.45 ± 0.01 (p < 0.001). The greatest increase in mean airway pressure was from 10.04 ± 0.03 cmH2O to 17.33 ± 0.03 cmH2O. Dissipated energy was significantly reduced with the device under all test conditions (p < 0.001). The greatest reduction in dissipated energy was from 1.74 ± 0.00 J to 0.84 ± 0.00 J per breath. The least reduction in dissipated energy was from 0.30 ± 0.00 J to 0.16 ± 0.00 J per breath. The greatest and least percentage reduction in dissipated energy was 68% and 33%, respectively.ConclusionsThe device bench tested in this study demonstrated a significant reduction in peak expiratory flow rate and dissipated energy, compared to ventilation with unregulated expiratory flow. Application of the device warrants further experimental and clinical evaluation.

Prospective Evaluation of a Modified Apnea Test in Brain Death Candidates that Does Not Require Disconnection from the Ventilator.

The apnea test (AT) is an important component in the determination of brain death/death by neurologic criteria (BD/DNC) and often entails disconnecting the patient from the ventilator followed by tracheal oxygen insufflation to ensure adequate oxygenation. To rate the test as positive, most international guidelines state that a lack of spontaneous breathing must be demonstrated when the arterial partial pressure of carbon dioxide (PaCO2)≥ 60mm Hg. However, the loss of positive end-expiratory pressure that is associated with disconnection from the ventilator may cause rapid desaturation. This, in turn, can lead to cardiopulmonary instability (especially in patients with pulmonary impairment and diseases such as acute respiratory distress syndrome), putting patients at increased risk. Therefore, this prospective study aimed to investigate whether a modified version of the AT (mAT), in which the patient remains connected to the ventilator, is a safer yet still valid alternative. The mAT was performed in all 140 BD/DNC candidates registered between January 2019 and December 2022: after 10min of preoxygenation, (1) positive end-expiratory pressure was increased by 2mbar (1.5mm Hg), (2) ventilation mode was switched to continuous positive airway pressure, and (3) apnea back-up mode was turned off (flow trigger 10 L/min). The mAT was considered positive when spontaneous breathing did not occur upon PaCO2 increase to ≥ 60mm Hg (baseline 35-45mm Hg). Clinical complications during/after mAT were documented. The mAT was possible in 139/140 patients and had a median duration of 15min (interquartile range 13-19min). Severe complications were not evident. In 51 patients, the post-mAT arterial partial pressure of oxygen (PaO2)was lower than the pre-mAT PaO2, whereas it was the same or higher in 88 cases. In patients with pulmonary impairment, apneic oxygenation during the mAT improved PaO2. In 123 cases, there was a transient drop in blood pressure at the end of or after the mAT, whereas in 12 cases, the mean arterial pressure dropped below 60mm Hg. The mAT is a safe and protective means of identifying patients who no longer have an intact central respiratory drive, which is a critical factor in the diagnosis of BD/DNC. Clinical trial registration DRKS, DRKS00017803, retrospectively registered 23.11.2020, https://drks.de/search/de/trial/DRKS00017803.

The effects of real-time waveform analysis software on patient ventilator synchronization during pressure support ventilation: a randomized crossover physiological study

BackgroundPatient-ventilator asynchrony commonly occurs during pressure support ventilation (PSV). IntelliSync + software (Hamilton Medical AG, Bonaduz, Switzerland) is a new ventilation technology that continuously analyzes ventilator waveforms to detect the beginning and end of patient inspiration in real time. This study aimed to evaluate the physiological effect of IntelliSync + software on inspiratory trigger delay time, delta airway (Paw) and esophageal (Pes) pressure drop during the trigger phase, airway occlusion pressure at 0.1 s (P0.1), and hemodynamic variables.MethodsA randomized crossover physiologic study was conducted in 14 mechanically ventilated patients under PSV. Patients were randomly assigned to receive conventional flow trigger and cycling, inspiratory trigger synchronization (I-sync), cycle synchronization (C-sync), and inspiratory trigger and cycle synchronization (I/C-sync) for 15 min at each step. Other ventilator settings were kept constant. Paw, Pes, airflow, P0.1, respiratory rate, SpO2, and hemodynamic variables were recorded. The primary outcome was inspiratory trigger and cycle delay time between each intervention. Secondary outcomes were delta Paw and Pes drop during the trigger phase, P0.1, SpO2, and hemodynamic variables.ResultsThe time to initiate the trigger was significantly shorter with I-sync compared to baseline (208.9±91.7 vs. 301.4±131.7 msec; P = 0.002) and I/C-sync compared to baseline (222.8±94.0 vs. 301.4±131.7 msec; P = 0.005). The I/C-sync group had significantly lower delta Paw and Pes drop during the trigger phase compared to C-sync group (-0.7±0.4 vs. -1.2±0.8 cmH2O; P = 0.028 and − 1.8±2.2 vs. -2.8±3.2 cmH2O; P = 0.011, respectively). No statistically significant differences were found in cycle delay time, P0.1 and other physiological variables between the groups.ConclusionsIntelliSync + software reduced inspiratory trigger delay time compared to the conventional flow trigger system during PSV mode. However, no significant improvements in cycle delay time and other physiological variables were observed with IntelliSync + software.Trial registrationThis study was registered in the Thai Clinical Trial Registry (TCTR20200528003; date of registration 28/05/2020).

Separation-induced transition on a T106A blade under low and elevated free stream turbulence

The separation-induced transition on the suction surface of a T106A low pressure turbine blade is a complex phenomenon with implications for aerodynamic performance. In this numerical investigation, we explore an adverse pressure gradient-dominated flow subjected to varying levels of free stream excitation, as the underlying separation-induced transition is a critical factor in assessing blade profile loss. By comprehensively analyzing the effects of free stream turbulence (FST) on the transition process, we delve into the various mechanisms which govern the instabilities underlying bypass transition by studying the instantaneous enstrophy field. This involves solving the two-dimensional (2D) compressible Navier–Stokes equation through a series of numerical simulations, comparing a baseline flow to cases where FST with varying turbulent intensity (Tu=4% and 7%) is imposed at the inflow. Consistent with previous studies, the introduction of FST is observed to delay flow separation and trigger early transition. We explore the different stages of bypass transition, from the initial growth of disturbances (described by linear stability theory) to the emergence of unsteady separation bubbles that merge into turbulent spots (due to nonlinear interactions), by examining the vorticity dynamics. Utilizing the compressible enstrophy transport equation for the flow in a T106A blade passage, we highlight the various routes of bypass transition resulting from different levels of FST, emphasizing the relative contributions from baroclinicity, compressibility, and viscous terms.

Respiratory mechanics analysis of inspiratory trigger in mechanical ventilation

To find out the circuit pressure and flow at the trigger point by observing the characteristics of the inspiratory trigger waveform of the ventilator, confirm the intra-alveolar pressure as the index to reflect the effort of the trigger according to the working principle of the ventilator combined with the laws of respiratory mechanics, establish the related mathematical formula, and analyze its influencing factors and logical relationship. A test-lung was connected to the circuit in a PB840 ventilator and a SV600 ventilator set in pressure-support mode. The positive end-expiratory pressure (PEEP) was set at 5 cmH2O (1 cmH2O ≈ 0.098 kPa), and the wall of test-lung was pulled outwards till an inspiratory was effectively triggered separately in slow, medium, fast power, and separately in flow-trigger mode (sensitivity VTrig 3 L/min, 5 L/min) and pressure-trigger mode (sensitivity PTrig 2 cmH2O, 4 cmH2O). By adjusting the scale of the curve in the ventilator display, the loop pressure and flow corresponding to the trigger point under different triggering conditions were observed. Taking intraalveolar pressure (Pa) as the research object, the Pa (called Pa-T) needed to reach the effective trigger time (TT) was analyzed in the method of respiratory mechanics, and the amplitude of pressure change (ΔP) and the time span (ΔT) of Pa during triggering were also analyzed. (1) Corresponding relationship between pressure and flow rate at TT time: in flow-trigger mode, in slow, medium and fast trigger, the inhalation flow rate was VTrig, and the circuit pressure was separately PEEP, PEEP-Pn, and PEEP-Pn' (Pn, Pn', being the decline range, and Pn' > Pn). In pressure-trigger mode, the inhalation flow rate was 1 L/min (PB840 ventilator) or 2 L/min (SV600 ventilator), and the circuit pressure was PEEP-PTrig. (2) Calculation of Pa-T: in flow-trigger mode, in slow trigger: Pa-T = PEEP-VTrigR (R represented airway resistance). In medium trigger: Pa-T = PEEP-Pn-VTrigR. In fast trigger: Pa-T = PEEP-Pn'-VTrigR. In pressure-trigger mode: Pa-T = PEEP-PTrig-1R. (3) Calculation of ΔP: in flow trigger mode, in flow trigger: without intrinsic PEEP (PEEPi), ΔP = VTrigR; with PEEPi, ΔP = PEEPi-PEEP+VTrigR. In medium trigger: without PEEPi, ΔP = Pn+VTrigR; with PEEPi, ΔP = PEEPi-PEEP+Pn+VTrigR. In fast trigger: without PEEPi, ΔP = Pn'+VTrigR; with PEEPi, ΔP = PEEPi-PEEP+Pn'+VTrigR. In pressure-trigger mode, without PEEPi, ΔP = PTrig+1R; with PEEPi, ΔP = PEEPi-PEEP+PTrig+1R. (4) Pressure time change rate of Pa (FP): FP = ΔP/ΔT. In the same ΔP, the shorter the ΔT, the greater the triggering ability. Similarly, in the same ΔT, the bigger the ΔP, the greater the triggering ability. The FP could better reflect the patient's triggering ability. The patient's inspiratory effort is reflected by three indicators: the minimum intrapulmonary pressure required for triggering, the pressure span of intrapulmonary pressure, and the pressure time change rate of intrapulmonary pressure, and formula is established, which can intuitively present the logical relationship between inspiratory trigger related factors and facilitate clinical analysis.

SMART Trigger versus Flow and Pressure trigger performance during auto-PEEP

Background Intrinsic positive end-expiratory pressure (auto-PEEP) is a common problem in mechanically ventilated patients, which can lead to adverse effects on patients comfort, hemodynamics, lung mechanics and gas exchange. Triggering systems play a crucial role in the delivery of mechanical ventilation, and advancements in smart triggering technology aim to optimize patient-ventilator synchrony. This bench study aims to compare the performance of the novel SMART Trigger to traditional pressure and flow triggers in the context of auto-PEEP. Methods A lung model simulating severe obstructive pattern with high compliance (80 ml/cmH2O) and high resistance 30 cmH2O/L/s was connected to the Panther 5 ventilator (Origin Medical, California, USA). The mode was set at Volume Controlled with a tidal volume of 700 ml and mandatory breath per min (BPM) of 10/min and Inspiratory time of 2 seconds to intentionally create auto-PEEP. Simulated spontaneous breaths set at 20 BPM with increasing muscle pressure (Pmus) from -1 to maximum of -25 or till full trigger of all breaths. Three different triggering systems were evaluated: SMART Trigger (ST sensitivity 1 to 7), pressure trigger (-1 cmH2O), and flow trigger (1 l/min). The range of auto-PEEP levels induced increased incrementally with the increase in the respiratory rate ranging from 3 cmH2O for 10 BPM, 8 for 15 BPM, to 13 for 20 BPM. The following parameters were assessed for each triggering system: trigger sensitivity (defined as the number of breaths triggered above the mandatory breaths), and the trigger response time (time it takes from the beginning of muscle effort to the initiation of the breath. Results 100% of the breaths were triggered at Pmus (cmH2O) of -15 in the pressure trigger, -25 in flow trigger, -3 for ST1, -9 for ST2, -10 for ST3, -10 for ST4, -12 for ST5, -18 for ST 6, and -22 for ST 7. Trigger time (msec) for flow was 0.135 ± 0.02, for pressure 0.141 ± 0.04, for ST 1-4: 0.076 ± 0.03, for ST 5-7: 0.104 ± 0.04. Multivariate analysis of variance test showed significant difference between the time to trigger P &lt;0.001. Conclusion This bench study highlights the potential advantages of SMART Trigger technology over conventional pressure and flow triggers during auto-PEEP. The SMART Trigger enhanced sensitivity and rapid response might contribute to improved patient-ventilator synchrony. Further research and clinical studies are warranted to validate these findings and explore the impact of smart trigger technology on patient outcomes in real-world scenarios. Keywords: SMART Trigger, Auto-PEEP, Trigger time

Automatic Apnea Time Adjustments During Ventilation With Automode.

Automode is a feature on Servo ventilators that automatically switches between mandatory and spontaneous breaths. Spontaneous breaths suppress mandatory breaths until apnea. The period from the last spontaneous breath to the first mandatory breath is automatically adjusted by a calculated apnea time limit based on a maximum apnea time setting, the mandatory breathing frequency setting, and the spontaneous breath count. The purpose of this study was to validate the apnea time algorithm by using simulated mechanical ventilation. A Servo-u ventilator was connected to an ASL 5000 breathing simulator. Ventilator settings were the following: Automode (pressure control to pressure support), pressure control = 10 cm H2O; pressure support = 5 cm H2O; PEEP = 10 cm H2O; breathing frequency = 10, 12, 15, 20 breaths/min; maximum apnea time = 7 and 12 s. Simulator settings were the following: resistance = 10 cm H2O/L/s; compliance = 35 mL/cm H2O; flow trigger model: frequency = 20 breaths/min, trigger flow = 10 L/min, trigger duration = 800 ms. Flow waveforms were recorded, and the observed apnea time limit was compared with the calculated value. The outcome variable was error, defined as the difference between observed and calculated apnea times expressed as a percentage. The observed apnea time limit ranged from 3 to 12 s, depending on the mandatory frequency and the spontaneous breath count. The average error ranged from -2 to 0%. The measured apnea time for simulated ventilation settings was within 2% of calculated times. Automode allowed a spontaneous frequency lower than expected based on the mandatory frequency.

Quality Control Patient Trigger Ventilator using Negative Air Pressure

This research aims to develop a quality control tool for patient trigger ventilators at PT Stechoq Robotika Indonesia. The increasing demand for ventilators has driven PT Stechoq Robotika Indonesia to create high-end ventilators. However, the production process faces challenges, particularly in the manual quality control of patient trigger alarms. Therefore, an automated quality control tool is needed to replace the manual mechanism. The research utilizes the Research and Development method. Trials are conducted on SIMV and CPAP modes with variations in pressure trigger and flow trigger parameters to evaluate the performance of patient trigger alarms on ventilators. The results of implementing the patient trigger quality control tool show an average accuracy rate of 70% for pressure and flow triggers in SIMV and CPAP modes. This tool is expected to reduce time and effort in the quality control process while improving the accuracy of triggering patient alarms on ventilators. Overall, the patient trigger ventilator quality control tool has significant potential in the ventilator industry, with positive implications for product quality and production efficiency at PT Stechoq Robotika Indonesia.

Identifying asynchronies: Delayed triggering

Patient-ventilator asynchronies can occur at any phase throughout the respiratory cycle. Because it has been associated with patient outcomes, it is important to recognize and address these asynchronies. Bedside interpretation of air flow and airway pressure waveforms are helpful for recognizing patient–ventilator asynchronies and optimizing ventilator settings. Patient effort is sensed by either a drop in circuit pressure (pressure trigger) or circuit bias flow (flow trigger). Triggering delay is the time interval between the start of the neural and mechanical inspiration. Triggers must be sensitive enough to recognize patient effort to avoid imposing an additional load but not too sensitive to avoid auto-triggering. Despite improvements in triggering technology, triggering asynchronies continue to occur and are manifest, among others, by delayed triggering. Keywords: asynchrony, patient effort, trigger, delayed triggering

Analysing the Large-Scale Debris Flow Event in July 2022 in Horlachtal, Austria Using Remote Sensing and Measurement Data

High-quality in situ measurements are essential for hazard assessment of debris flow events. However, precise data on debris flow triggering thresholds, accumulation volumes and spatial characteristics of large-scale events on catchment scale are scarce due to the rare occurrence of debris flows and the challenges of acquiring accurate data for a larger area. In this study, we present quantitative analyses of a single extreme debris flow event in the Horlachtal, Austria, triggered by local high-intensity short-duration precipitation events on 20 and 23 July 2022. Pre- and post-event airborne LiDAR (light detection and ranging) data with a high spatial resolution reveal that 156 different debris flow processes were initiated during these events, with accumulation volumes of up to approximately 40,000 m³. The calculated debris flow deposition volumes also show a power-law relationship with the total amount of rainfall in the respective debris flow catchments. The spatial appearance of the debris flows shows a concentration of processes in a particular area rather than a uniform distribution, suggesting a local nature of the triggering event. This is further supported by the measurements from three meteorological stations and four discharge gauges within the study area. The gridded area-wide INCA (Integrated Nowcasting through Comprehensive Analysis) rainfall data further point to a local convective event on 20 July 2022, with a maximum rainfall intensity of 44 mm/h.

The structure of a magnitude-frequency relation for debris flows conditioned by earthquake shock

Debris flow is a major secondary geological process associated with the 2008 M7.9 Wenchuan Earthquake area, causing the loss of around 200 lives as well as extensive property damage. Based on data developed over the past 21 years (1998–2018) of continuous monitoring of debris flow events in Sichuan, the temporal and spatial aspects of debris flows have been analyzed, including magnitude and frequency. The 21-year study period is divided into three time-intervals: 1998–2007 (pre-earthquake), 2008–2013 (short-term post-earthquake), and 2014–2018 (long-term post-earthquake). Distribution maps are plotted to compare debris flow distribution density in the three periods and to visualize debris flow development throughout Sichuan Province from 1998 to 2018. Many large-scale debris flows occur in groups immediately following the earthquake (2008–2013). After 2014, the magnitude and frequency of debris flows begin to decrease and gradually returned near to the pre-earthquake level as the damaged landscape recovered. The effect of rainfall is investigated by analyzing a 21-year record of precipitation; Following the earthquake the threshold rainfall values for debris flow triggering decrease only to recover to pre-earthquake levels as the landscape heals. Magnitude-frequency (M-F) relations for debris flows of the three periods were developed, and the distribution can be well fitted by a power-law function. Finally, the work done by debris flow was defined by multiplying the magnitude by frequency. At the regional scale, the work peaks in the three time periods have been determined and it is found that the peaks corresponded with the larger debris flow sizes. The concept of offset is introduced to describe the shift of the work peak in relation to the probability peak and is termed the Wolman-Miller offset. It is concluded that with a greater offset in the short-term post-earthquake period, more work has been done by larger events and that the greater proportion of the volume being mobilized by larger events occurring more frequently is a key process in the landscape returning to a pre-earthquake (equilibrium) state. The recovery of an earthquake-damaged landscape represents a transient period of high hazard that should be considered in any hazard assessment of earthquake-triggered landslides (in addition to co-seismic landslides).

Establishing a record of extreme debris flow events in a high Alpine catchment since the end of the Little Ice Age using lichenometric dating

ABSTRACT Establishing a record of large debris flow events in high Alpine areas prior to the availability of high resolution remote sensing data can be very challenging. In this study, we investigate the debris flow activity in two tributary valleys of the Horlachtal catchment in Tyrol, Austria between the end of the Little Ice Age at about 1850 and the first available area wide aerial images from 1947. To accomplish this, we calculated a local lichenometric calibration curve using the long axis diameters of the five largest Rhizocarpon lichen thalli at 51 different reference locations. Because of the interval-censored dating of most of the reference sites, we established a bootstrapping approach within the calibration curve calculation process. With the help of the lichenometric calibration data, we were able to date 47 old debris flow deposits in the study area. The results indicate no increasing or decreasing trends in frequencies of extreme debris flow events. In addition, the results point to a very local character of debris flow triggering precipitation events, as we can detect major differences in neighbouring valleys. Lichenometric derived datings also provide temporal informations about the end of debris flow activity at some sites in the study area and thus can contribute to a better understanding of debris flow systems.

Definition of Rainfall Thresholds for Shallow Landslides in Colombian Tropical Mountainous Catchments as Debris Flow Triggering Mechanism

As a cascade precursor of the Debris Flow phenomenon, landslides generate economic losses and human fatalities worldwide, especially in mountainous and tropical countries like Colombia. This work proposes two different methodologies of defining rainfall thresholds as a tool for Early Warning Systems for Debris Flow occurrence in Colombian urban and mountainous catchments: Empirical-Statistical and Physically based. Empirical-Statistical rainfall thresholds are defined using several data sources such as rain gauges (pluviometers), radar, and satellite data allowing a different timing and spatial resolution in the definition. The definition of physically based rainfall thresholds the TRIGRS software is used in mountainous catchments with rainfall data from rain gauges, with the information from the safety factor map resulting in the simulations calculated as the cumulative density function from the histogram of the distributed safety factor allowing the understanding of how the instability varies in a catchment during different storms events

Monitoring the role of soil hydrologic conditions and rainfall for the triggering of torrential flows in the Rebaixader catchment (Central Pyrenees, Spain)

Torrential flows (debris flows and debris floods) are mainly triggered by precipitation and soil hydrological processes. Most early warning systems in torrential catchments are rainfall-based. However, this approach can result in frequent false positives, due to its pure black-box nature, in which soil water conditions are neglected. We aim to contribute to the understanding of the conditions required for triggering torrential flows by considering also in situ measurements of soil water content. Herein, monitoring data of 12 years of rainfall and torrential flow occurrence (2009–2020) and 8 years of soil hydrologic conditions (2013–2020) in the Rebaixader catchment (Central Pyrenees, Spain) are analyzed. The dataset includes more than 1000 rainfall events and 37 torrential flows. First, rainfall thresholds using maximum rainfall intensity (Imax) and mean intensity (Imean) are defined. For the 2013–2020 dataset, which includes 15 torrential events, the Imean threshold predicted 2 false negatives and 73 false positives (positive predictive value, PPV, of 15.1%) and the best Imax threshold predicted also 2 false negatives but only 11 false positives (PPV of 54.2%). However, our observations confirmed quantitatively that the lower is the soil moisture the higher is the rainfall intensity to trigger torrential flows. Then, we combined Imax and volumetric water content at 15 and 30 cm depth to define a hydro-meteorological threshold. This latter threshold reduced false negatives to 1 and false positives to 8 and increased the PPV to 63.6%. These results confirm that soil hydrological conditions are key factors for torrential flow triggering and may improve early-warning predictions.

English as a Foreign Language Teacher Flow: How Do Personality and Emotional Intelligence Factor in?

Teaching is one of the professions that creates opportunities for individuals to experience flow, a state of complete absorption in an activity. However, very few studies have examined ESL/EFL teachers’ flow states inside or outside the classroom. As such, this study aimed to explore the quality of experience of 75 EFL teachers in flow and also examine the relationships between their emotional intelligence, the Big Five personality traits and the flow state. To this end, the teachers filled out recurrent flow surveys for a week, and also completed emotional intelligence and the Big Five personality questionnaires. It was found that reading was the major flow trigger outside the classroom and teaching and delivering lessons was the most significant flow-inducing activity for the teachers inside the classroom. Furthermore, correlations and independent samples t-tests indicated that all emotional intelligence and personality traits had significant relationships with flow except agreeableness. Finally, multiple regression analysis showed that two personality traits, conscientiousness and openness to experience were the strongest predictors of the flow state. The implications for future flow-related research in the field of applied linguistics are discussed.

Analysis of Debris Flow Triggering Conditions for Different Rainfall Patterns Based on Satellite Rainfall Products in Hengduan Mountain Region, China

Rainfall is the main factor that induces debris flow. Satellite rainfall products provide a new source of data in terms of debris flow-triggering conditions to overcome the lack of rainfall data coverage from ground-based rainfall gauges in large-scale mountainous regions. In this study, the applicability of four satellite rainfall products (CMORPH, GPM, MSWEP, and PERSIANN) in the Hengduan Mountain region (HMR) was evaluated with reference to ground observation data from 2000 to 2020. The critical rainfall and rainfall thresholds under different rainfall patterns and warning levels that trigger debris flows were analyzed according to the empirical cumulative distribution function (ECDF) and cumulative probability. The results showed that CMORPH (comprehensive indicator score (CI = 0.72) and GPM (CI = 0.70) performed better in the simulation of daily rainfall sequence consistency and extreme rainfall conditions in the study area. CMORPH also had the highest reconstruction rate for correctly capturing rainfall events that triggered debris flows, with a value of 89%. Approximately half of the rainfall patterns that cause debris flows are antecedent-effective-rainfall-dominated. Both intraday-rainfall-dominated and intraday-antecedent-rainfall-balanced patterns were below 30%. There were evident differences in the critical rainfall for different rainfall patterns under the same warning level. By comparing the results of previous studies on rainfall thresholds, it is believed that the results of this study confirm the application of satellite rainfall products; in addition, the calculated rainfall thresholds can provide a reference for the early warning of debris flows in the HMR. In general, this work is of great significance to the prediction and early warning of debris flow hazards.

Delayed tracheal extubation after cardiac surgery due to cardiogenic ventilator auto-triggering: a case report

BackgroundVentilator auto-triggering is associated with poor outcomes. Herein, we present a case of delayed tracheal extubation after cardiac surgery due to cardiogenic auto-triggering.Case presentationA 73-year-old male with chronic constrictive pericarditis underwent radical pericardiectomy. After confirming hemodynamic stability, we conducted spontaneous breathing trial (SBT) with a flow-trigger sensitivity of 1 L/min. As his respiratory rate (RR) increased to more than 60 breaths/min and tidal volume decreased to less than 100 mL, this SBT was considered a failure. Next morning, SBT was reperformed and the result was unchanged. However, we noticed that his heart rate and RR were the same and suspected auto-triggering caused by cardiogenic oscillations. We changed ventilator mode from flow triggering to pressure triggering of −2 cmH2O and he was uneventfully extubated.ConclusionWe experienced a case of delayed tracheal extubation after cardiac surgery due to cardiogenic auto-triggering. Auto-triggering can be reduced by changing ventilator trigger mode.

Neuroinflammation in Ischemic Stroke: Inhibition of cAMP-Specific Phosphodiesterases (PDEs) to the Rescue.

Ischemic stroke is caused by a thromboembolic occlusion of a major cerebral artery, with the impaired blood flow triggering neuroinflammation and subsequent neuronal damage. Both the innate immune system (e.g., neutrophils, monocytes/macrophages) in the acute ischemic stroke phase and the adaptive immune system (e.g., T cells, B cells) in the chronic phase contribute to this neuroinflammatory process. Considering that the available therapeutic strategies are insufficiently successful, there is an urgent need for novel treatment options. It has been shown that increasing cAMP levels lowers neuroinflammation. By inhibiting cAMP-specific phosphodiesterases (PDEs), i.e., PDE4, 7, and 8, neuroinflammation can be tempered through elevating cAMP levels and, thereby, this can induce an improved functional recovery. This review discusses recent preclinical findings, clinical implications, and future perspectives of cAMP-specific PDE inhibition as a novel research interest for the treatment of ischemic stroke. In particular, PDE4 inhibition has been extensively studied, and is promising for the treatment of acute neuroinflammation following a stroke, whereas PDE7 and 8 inhibition more target the T cell component. In addition, more targeted PDE4 gene inhibition, or combined PDE4 and PDE7 or 8 inhibition, requires more extensive research.

Comparison of different methods of obtaining the rapid shallow breathing index

ObjectiveTo compare the Rapid Shallow Breathing Index (RSBI) obtained by the ventilometer and from mechanical ventilation parameters. MethodsRandomized crossover trial, including 33 intubated patients, on mechanical ventilation for at least 24 hours, undergoing spontaneous breathing test. Patients were submitted to the measurement of RSBI by four methods: disconnected from the ventilator through the ventilometer; in Pressure Support Ventilation (PSV) mode at a pressure of 7.ßcm H2O; in Continuous Positive Airway Pressure (CPAP) mode at a pressure of 5.ßcmH2O with flow trigger; in CPAP mode at a pressure of 5.ßcmH2O with pressure trigger. ResultsNo significant difference was detected between the RSBI obtained by the ventilometer and in the CPAP mode with flow and pressure triggers, however, in the PSV mode, the values were lower than in the other measurements (p.ß<.ß0.001). By selecting patients from the sample with higher RSBI (... 80 cycles.min-1.L-1), the value of the index obtained by the ventilometer was higher than that obtained in the three options of ventilation methods. ConclusionThe RSBI obtained in the CPAP mode at a pressure of 5.ßcmH2O, in both triggers types, did not differ from that measured by the ventilometer; it is, therefore, an alternative when obtaining it from mechanical ventilation parameters is necessary. However, in the presence of borderline values, the RSBI measured by ventilometer is recommended, as in this method the values are significantly higher than in the three ventilation modalities investigated.

Analysis of the rainfall pattern triggering the Lemešná debris flow, Javorníky Range, the Czech Republic

Two significant rainfall episodes affected the eastern part of the Czech Republic in May 2010 causing dozens of landslides, including a potentially damaging debris flow on Lemesna Mt. in the Javorniky Range on the 2 June 2010. The rainfall data from the rainfall gauges managed by the Czech Hydrometeorological Institute situated 7, 12 and 20 km from the debris flow were analysed and a new rainfall gauge was installed in the immediate vicinity of the debris flow. The following rainfall parameters were calculated as moving values for each day within the period from 1983 to 2018: cumulative rainfall of 2, 3, 5, 10, 20, 30, 60 days and an antecedent precipitation index of 5, 10, 20, 30, 60 days. The rainfall totals, which exceeded the debris flow triggering precipitation by many times, but no slope deformation was recorded during them, were also analysed. The debris flow triggering rainfall values were assessed and they showed a single concordance of all of the tested rainfall parameters on the day of the debris flow. We found that the combination of cumulative rainfall for 30 days together with 1-day and 3-day amounts, overall rainfall pattern and the development of the rainfall situation were more important for triggering the Lemesna debris flow than the individual rainfall extremes. This provides a new perspective to the rainfall thresholds issue. The importance of choosing the calculating method between the cumulative rainfalls and the antecedent precipitation index is illustrated by the significant differences between the values. The significance of the rainfall gauge selection is also emphasised, since the orographic position together with the distance between gauges can significantly influence the differences between on-site and measured rainfall amounts.